Photovoltaic cells provide clean, non-polluting energy by converting light, either natural sunlight or artificial light, into electricity. Photovoltaic cell efficiency has increased, but photovoltaic cells still do not convert 100% of available light into electricity. At best, photovoltaic cells in a laboratory environment may convert 50% of light into electricity. Commercially available photovoltaic cells may have an efficiency closer to 30%. Photovoltaic cell efficiency is dependent on, for example, the chemical makeup of the photovoltaic cell, the wavelengths of light that reach the photovoltaic cell, and the temperature of the photovoltaic cell.
Photovoltaic cells may have a range of efficiency, and may not convert the entire light spectrum into electricity with equal efficiency. Photovoltaic cells may only convert discrete wavelengths or ranges of wavelengths of light energy into electricity, and may not convert certain wavelengths of light energy into electricity at all. For example, some photovoltaic cells may not convert visible light into electricity. Additionally, different photovoltaic cell compositions may be more efficient at converting different wavelengths of light energy into electricity. For example, silicon photovoltaic cells may be most efficient (i.e., convert the largest percentage of available light energy into electricity) when the wavelength of light is approximately 980-1180 nanometers. Gallium arsenide photovoltaic cells may be most efficient at a different wavelength range. Photovoltaic cells may also work most efficiently in a certain range of operating temperatures. A photovoltaic cell may be most efficient at, for example, 70 degrees Fahrenheit, and may not be as efficient at, for example, −20 degrees Fahrenheit or at 100 degrees Fahrenheit.
Light which is not converted to electricity may be absorbed, reflected, or transmitted through the photovoltaic cell. Light energy absorbed by the photovoltaic cell but not converted into electricity may be converted into heat energy. This heat energy may warm the photovoltaic cell, and may move the photovoltaic cell out of the optimum temperature range for maximum efficiency. This decreased efficiency may not be desirable from an operational standpoint, or may even adversely affect the lifespan of the photovoltaic cell.